Example showing the life stages of a holometabolous moth
(www.sas.upenn.edu/~tait/gragonfliesandbutterfles.html)
Sesamia grisescens is a holometabolous insect.
The life cycle of Sesamia grisescens takes 60-70 days from egg to adult. Populations are highly discrete at RAMU with level and physical peaks every 6-8 weeks. There are 5.5 generations in one year and the highest number of larvae occur in April/May when they impart most damage to the crop.
Oviposition One adult female moth oviposits its mass of eggs (120) under the green leaf sheaths of 2-6 months old canes. Oviposition time: between 9.00 p.m. and 11.00 p.m. Oviposition lasts for one hour with egg masses being aligned on the leaf sheaths in 2-3 batches. Eggs take 9 days to hatch.
Primary Feeding The 1st instar larvae eat the egg remnants and bore into soft leaf sheaths and feed gregariously on mesophyll tissues for two days and then shifts into the internodes towards the meristem. They continue to feed on the tissues for 8-10 days until the apical meristem is killed. Gradually (11 days after hatching), it leads to the well known 'Dead Heart' symptom identified by brown shrivelled spindle.
Secondary Feeding 4th and 5th instars larvae jump to nearby stalks and tunnel through the upper internodes. The final instars tunnel down the internode for another 20 days, make a hole into the stem, plugs it with frass and pupate within at 40-100mm.
Pupation on leaf sheath may also occur. On average pupation time is 17 days (8-21 days), though females are faster to emerge. Adult Moths are nocturnal and hide in cane trash during the day. The lifespan of adults under laboratory conditions were seven days. Normal emergence time: between 7.30 p.m. and 9.00 p.m. (Young & Kuniata 1992)
Mating patterns
Females release pheromones to attract males
Mating occurs only on the night of emergence
Moths become active one hour before sunrise. Females flutter their wings in call for mating while standing vertically on stalks or leaves. Males fly or walk towards the females to mate.